JUMA Amateur Radio Forum

Whilst assisting an amateur who is experiencing some problems getting his kit to work, I made some measurements on my transceiver to show the sort of waveforms and signal levels you are likely to encounter. For these measurements, the transceiver was set to 1.8MHz, as even a fairly modest oscillosco...

Juma TRX-2 Firmware, Version: 3.00a Build 24. Build 23 has been removed. As a result of a minor code move to resolve an internal low-level annoyance, I accidentally omitted the offset cancelation in the TX mode, and thus the CW/CWR/RIT offset from the RX mode was still present in the TX mode. My sin...

Hi, Whitney, Yes, you are correct, there are no pads on any of the printed circuit boards that are specifically intended as test points. Nevertheless, by examining the various schematics and their printed circuit layouts you will find plenty of places where an oscilloscope probe or a multi-meter tes...

This build introduces an additional feature to the CW Practice Mode, and finally cures all the switching glitches. CW Practice Mode It is now possible to select the LCD scroll direction. To enter the CW Practice Mode, from the power off state, press and hold the FILTER button, and briefly press the ...

Hi, OK, now you have the microprocessor working it sounds as if the DDS is not working. If you connect any sort of antenna to the input of the receiver, it is sufficiently sensitive that you should hear lots of signals. If all you hear is noise, this suggests that the synthesiser is not working, or ...

Build 3 - 26/MAR/2017 Build 1 has been removed, and replaced with Build 3. Whilst playing around with the remote commands I discovered that if the manual band change command was incorrectly formatted, then an erroneous display would result. This version of the firmware uses more robust error checkin...

Hi, Erich, OK, that explains your symptoms. Note that R11/R12 and R23/R24 are 0.22 Ohms each, so that their parallel combination is 0.11 Ohms. They provide a small amount of DC negative feedback, but their primary function is that of providing a means of measuring the currents through the driver and...

Hi, Erich, I am somewhat confused by your description. Let's see if we can resolve this. First, the pots must be multi-turn, a single-turn pot adjustment is far too coarse to allow for a nice fine smooth adjustment, so your damaged pot will have to be replaced with a 10-turn unit. As for your adjust...

Hi, Glen, If you loaded my firmware using the PicKit-3 and MPLAB IDE, then as the flash-writer is not present in this HEX file, you will not get it to run. As you have discovered, it is quite easy to flash the microprocessor using the 6-pin ICD header, and, as long as you are quite happy to make any...

Good morning, Erich, Glad that you have managed to remove the transistors without damaging the board. There are some other checks that you should perform to ensure that your replacement transistors do not fail. 1. Bias Supply If there is a fault in the bias supply, this can cause excessive bias curr...